JunHyuk Song
Radha Poovendran
University of Washington
Jicheol Lee
INTERNET DRAFT Samsung Electronics
Expires: May 30, August 2, 2006 February 3 2006 November 30 2005
The AES-CMAC-96 Algorithm and its use with IPsec
draft-songlee-aes-cmac-96-03.txt
draft-songlee-aes-cmac-96-04.txt
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Copyright (C) The Internet Society (2005). (2006).
Abstract
National Institute of Standards and Technology (NIST) has newly
specified the Cipher based MAC (CMAC) which is equivalent to the
One-Key CBC-MAC1 (OMAC1) algorithm submitted by Iwata and Kurosawa.
OMAC1 efficiently reduces the key size of Extended Cipher Block
Chaining mode (XCBC). This memo specifies the use of CMAC mode on
authentication mechanism of IPsec Encapsulating Security Payload
(ESP) and the Authentication Header (AH) protocols. This new
algorithm is named AES-CMAC-96.
1. Introduction
National Institute of Standards and Technology (NIST) has newly
specified the Cipher-based Message Authentication Code (CMAC).
CMAC [NIST-CMAC] is a keyed hash function message authentication code that is based on
a symmetric key block cipher such as the Advanced Encryption
Standard [NIST-AES]. CMAC is equivalent to the One-Key CBC MAC1
(OMAC1) submitted by Iwata and Kurosawa [OMAC1a, OMAC1b]. OMAC1
is an improvement of the eXtended Cipher Block Chaining mode (XCBC)
submitted by Black and Rogaway [XCBCa, XCBCb], which itself is an
improvement of the basic CBC-MAC. XCBC efficiently addresses the
security deficiencies of CBC-MAC, and OMAC1 efficiently reduces the
key size of XCBC.
This memo specifies the usage of CMAC on authentication mechanism
of IPsec Encapsulating Security Payload (ESP) [ESP] and the
Authentication Header (AH) protocols. This new algorithm is named
AES-CMAC-96. For further information on AH and ESP, refer to [AH]
and [ROADMAP].
2. Basic definitions
CBC Cipher Block Chaining mode of operation for message
authentication code.
MAC Message Authentication Code.
A bit string of a fixed length, computed by MAC
generation algorithm, that is used to established
the authority and hence, the integrity of a message.
CMAC Cipher-based MAC based on an approved symmetric key
block cipher, such as the Advanced Encryption
Standard.
Key (K) 128-bits (16bytes) (16 octets) long key for AES-128 cipher
block. Denoted by K.
Message (M) Message to be authenticated.
Denoted by M.
Length (len) The length of message M in bytes. octets.
Denoted by len.
Minimum value of the length can be 0. The maximum
value of the length is not specified in this document.
truncate(T,l) Truncate T (MAC) in msb-first order with l bytes. octet.
T The output of AES-CMAC
Truncated T The truncated output of AES-CMAC-128 in MSB first
order.
AES-CMAC CMAC generation function based on AES block cipher
with 128-bits key
AES-CMAC-96 IPsec AH and ESP MAC generation function based on
AES-CMAC which truncates MSB 96 bits of 128 bits
output
3. AES-CMAC
The core of AES-CMAC-96 is the AES-CMAC [AES-CMAC]. The underlying
algorithm for AES-CMAC are Advanced Encryption Standard cipher block
[AES] and recently defined CMAC mode of operation [NIST-CMAC].
AES-CMAC provides stronger assurance of data integrity than a
checksum or an error detecting code. The verification of a checksum
or an error detecting code detects only accidental modifications of
the data, while CMAC is designed to detect intentional, unauthorized
modifications of the data, as well as accidental modifications. The
output of AES-CMAC can validate the input message. Validating the
message provide assurance of the integrity and authenticity over the
message from the source. According to [NIST-CMAC] at least 64-bits
should be used for against guessing attack. AES-CMAC achieves the
similar security goal of HMAC [RFC-HMAC]. Since AES-CMAC is based
on a symmetric key block cipher, AES, while HMAC is based on a hash
function, such as SHA-1, AES-CMAC is appropriate for information
systems in which AES is more readily available than a hash function.
For detail information about AES-CMAC is available in [AES-CMAC] and
[NIST-CMAC].
4. AES-CMAC-96
For use in IPsec message authentication on AH and ESP, AES-CMAC-96
should be used. AES-CMAC-96 is a AES-CMAC with 96-bit-long truncated
output in most significant bit first order. The output of 96 bits
MAC that will meet the default authenticator length as specified
in [AH]. The result of truncation should be is taken in most significant bits
first order. For further information on AES-CMAC, refer to
[AES-CMAC] and [NIST-CMAC].
Figure 1 describes AES-CMAC-96 algorithm:
In step 1, AES-CMAC is applied to the message 'M' in length 'len'
with key 'K'
In step 2, Truncate output block, T with 12 byte octets in
msb-first-order and return TT.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Algorithm AES-CMAC-96 +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ +
+ Input : K (128-bit Key described in section 4.1) +
+ : M ( message to be authenticated ) +
+ : len ( length of message in bytes octets ) +
+ Output : Truncated T (Truncated output with length 12 bytes) + octets)+
+ +
+-------------------------------------------------------------------+
+ +
+ Step 1. T := AES-CMAC (K,M,len); +
+ Step 2. TT := truncate (T, 12); +
+ return TT; +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Figure 1 Algorithm AES-CMAC-96
5. Test Vectors
These test cases same as defined in [NIST-CMAC] with one exception of
96 bits truncation
--------------------------------------------------
K 2b7e1516 28aed2a6 abf71588 09cf4f3c
Subkey Generation
AES_128(key,0) 7df76b0c 1ab899b3 3e42f047 b91b546f
K1 fbeed618 35713366 7c85e08f 7236a8de
K2 f7ddac30 6ae266cc f90bc11e e46d513b
Test Case 1: len = 0
M <empty string>
AES_CMAC_96 bb1d6929 e9593728 7fa37d12
Test Case 2: len = 16
M 6bc1bee2 2e409f96 e93d7e11 7393172a
AES_CMAC_96 070a16b4 6b4d4144 f79bdd9d
Test Case 3: len = 40
M 6bc1bee2 2e409f96 e93d7e11 7393172a
ae2d8a57 1e03ac9c 9eb76fac 45af8e51
30c81c46 a35ce411
AES_CMAC_96 dfa66747 de9ae630 30ca3261
Test Case 4: len = 64
M 6bc1bee2 2e409f96 e93d7e11 7393172a
ae2d8a57 1e03ac9c 9eb76fac 45af8e51
30c81c46 a35ce411 e5fbc119 1a0a52ef
f69f2445 df4f9b17 ad2b417b e66c3710
AES_CMAC_96 51f0bebf 7e3b9d92 fc497417
--------------------------------------------------
6. Interaction with the ESP Cipher Mechanism
As of this writing, there are no known issues which preclude the use
of AES-CMAC-96 with any specific cipher algorithm.
7. Security Considerations
See security consideration of [AES-CMAC].
8. IANA Consideration
IANA should allocate a value for IKEv2 Transform Type 3 (Integrity
Algorithm) to the AES-CMAC-PRF-128 AUTH_AES_CMAC_96 algorithm when this document is
published.
9. Acknowledgement
Portions of this text were borrowed from [NIST-CMAC] and
[AES-XCBC-MAC]. We would like to thank to Russ Housley for his
useful comments.
10. References
10.1. Normative References
[NIST-CMAC] NIST, Special Publication 800-38B Draft,"Recommendation
for Block Cipher Modes of Operation: The CMAC Method
for Authentication," March 9, 2005
[NIST-AES] NIST, FIPS 197, "Advanced Encryption Standard (AES),"
November 2001.
http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
[OMAC1] "OMAC: One-Key CBC MAC," Tetsu Iwata and Kaoru Kurosawa,
Department of Computer and Information Sciences,
Ilbaraki University, March 10, 2003.
[ESP] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[XCBC] Black, J. and P. Rogaway, "A Suggestion for Handling
Arbitrary-Length Messages with the CBC MAC," NIST
Second Modes of Operation Workshop, August 2001.
http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/
xcbc-mac/xcbc-mac-spec.pdf
[AES-CMAC] JunHyuk Song, Jicheol Lee, Radha Poovendran, Tetsu Iwata
"The AES-CMAC Algorithm" draft-songlee-aes-cmac-02.txt,
October 2005 (Work in progress)
10.2. Informative References
[AH] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[ROADMAP] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security
Document Roadmap", RFC 2411, November 1998.
[OMAC1a] Tetsu Iwata and Kaoru Kurosawa, "OMAC: One-Key CBC MAC,"
Fast Software Encryption, FSE 2003, LNCS 2887,
pp. 129-153, Springer-Verlag, 2003.
[RFC-HMAC] Hugo Krawczyk, Mihir Bellare and Ran Canetti,
"HMAC: Keyed-Hashing for Message Authentication,"
RFC2104, February 1997.
[OMAC1] "OMAC: One-Key CBC MAC," Tetsu Iwata and Kaoru Kurosawa,
Department of Computer and Information Sciences,
Ilbaraki University, March 10, 2003.
[OMAC1b] Tetsu Iwata and Kaoru Kurosawa, "OMAC: One-Key CBC MAC,"
Submission to NIST, December 2002.
Available from the NIST modes of operation web site at
http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/
omac/omac-spec.pdf
[XCBCa] John Black and Phillip Rogaway, "A Suggestion for
Handling Arbitrary-Length Messages with the CBC MAC,"
NIST Second Modes of Operation Workshop, August 2001.
Available from the NIST modes of operation web site at
http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/
xcbc-mac/xcbc-mac-spec.pdf
[XCBCb] John Black and Phillip Rogaway, "CBC MACs for
Arbitrary-Length Messages: The Three-Key
Constructions," Journal of Cryptology, Vol. 18, No. 2,
pp. 111-132, Springer-Verlag, Spring 2005.
[XCBC] Black, J. and P. Rogaway, "A Suggestion for Handling
Arbitrary-Length Messages with the CBC MAC," NIST
Second Modes of Operation Workshop, August 2001.
http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/
xcbc-mac/xcbc-mac-spec.pdf
[IKEv2] Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
Protocol", draft-ietf-ipsec-ikev2-17
(work in progress), September 2004.
11. Author's Address
Junhyuk Song
University of Washington
Samsung Electronics
(206) 853-5843
songlee@ee.washington.edu
junhyuk.song@samsung.com
Jicheol Lee
Samsung Electronics
+82-31-279-3605
jicheol.lee@samsung.com
Radha Poovendran
Network Security Lab (NSL)
Dept. of Electrical Engineering
University of Washington
(206) 221-6512
radha@ee.washington.edu
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